Introduction to Burns

Original Editor - Carin Hunter based on the course by [TUTOR LINK/ PhysioPlus ReLab]
Top Contributors - Carin Hunter, Jess Bell, Stacy Schiurring, Kim Jackson and Nikhil Benhur Abburi

What is a Burn?

A burn is an injury to the skin or other organic tissue primarily caused by exposure to heat or other causative agents (radiation, electricity, chemicals). According to WHO, it is a  global public health problem, accounting for an estimated 180,000 deaths annually. It is among the leading causes of disability in low and middle-income countries and almost two-thirds occur in the WHO African and South-East Asia regions. Burns do not only affect the skin, they can have other effects on the tissue, organ and system networks such as smoke inhalation, as well as psychological effects. Burns affect all genders although females have slightly higher rates of death from burns compared to males. They also affect all age groups and are the fifth most common cause of non-fatal childhood injuries.

Types of Burns

1. Thermal

Thermal burn injuries are caused by exposure to an external heat source or hot liquids. An external heat source can be a hot solid objects or even a cold object. Scalds are caused by wet substances, hot water, steam from hot water or cold water. The types of thermal burns are:

Flame Burns

Flame burns are caused by an exposure to an open fire. These are often associated with an inhalation injury and trauma. They tend to be mostly deep dermal or full-thickness burns. Flame burns are commonly found in adults but, they are also associated with abuse in children, domestic violence and certain rituals.

Contact Burns

Contact Burns are caused by contact with an extremely hot object or surface, commonly seem with stoves, heaters and irons. Contact burns tend to be deep dermal or full-thickness burns. They are commonly seen in people with epilepsy, those who misuse addictive substances or in elderly people after a loss of consciousness.

Frostbite or Ice Burns

Frostbite occurs when the skin is exposed to cold, typically any temperature below -0.55C (31F), for an extended period of time. This causes the water in the cells of the skin and underlying tissue to freeze and crystalise. An individual can suffer an injury from this crystallisation or indirectly from the tissue becoming ischemic. Frostbite can affect any part of your body, but the extremities, such as the hands, feet, ears, nose and lips, are most likely to be affected. If frostbite penetrates the deeper skin layers, impacting tissue and bone, it can cause permanent damage.

An Ice or Snow Burn is caused by ice or something very cold touching your skin for an extended period of time. Prolonged exposure to freezing temperatures, snow, or high-velocity winds can increase the chance of this type of burn. Ice burns are commonly caused by ice or cold packs being pressed directly against the skin when treating an injury or sore muscles.

Scalds

Scalds are caused by hot liquids. Commonly encountered liquids in this category are boiling water and cooking oil. Common mechanisms of injury is spilling of a hot drink or cooking oil or being exposed to hot bath water. Scalds tend to cause superficial to superficial partial burns. Scald burns result in about 70% of burns in children. They also often occur in elderly people.

2. Electrical burn, e.g. electrocution

An electrical burn is an injury caused by heat produced when an electrical current passes through a body. This can cause deep tissue injuries. The injury severity depends on many factors, the main ones being the pathway of the current, the resistance of the current in the tissues, and the strength and duration of the flow. Neither AC (Alternating Current) or DC (Direct Current) are more dangerous. But they can present with different symptoms. Patients that suffer from injuries with DC current, often cannot pull themselves away causing the duration of the injury to continue for longer. Electrical Burns are often associated with cardiac arrest, ventricular fibrillation, and tetanic muscle contractions.

For more information, please see AC and DC Electric Shock Effects Compared

3. Chemical Burns, e.g. Hydrofluoric Acid

Chemical burns or Caustic Burns are injuries cause by skin coming into direct contact with a chemical agent. These can be strong acids, alkaline, or organic compounds. Chemical compounds can have different effects on human tissue depending on the following:

• The strength or concentration of the chemical
• The site of contact (eye, skin, mucous membrane)
• Ingestion or inhalation
• Skin integrity
• Volume of substance
• Duration of exposure
• Chemical process
  • Acids can causes "coagulation necrosis" of the tissue.
  • Alkaline burns can cause "liquefaction necrosis".

4. Radiation burn

Radiation burn is damage due to prolonged exposure to radiation. The most common type of radiation burn is sunburn caused by prolonged exposure to Ultraviolet rays (UV). High exposure to radiotherapy can also cause erythema, known as radiation burns. These are often associated with cancer due to the ability of ionising radiation to interact with and damage DNA.

5. Inhalation Burns/Injury

Inhalation injury refers to pulmonary injury resulting from inhalation of smoke or chemical products of combustion. Inhalation injury results in direct cellular damage, alterations in regional blood circulation and perfusion, obstruction of the airways, and the release of pro-inflammatory cytokine and toxin release. Inhalation injuries also causes reduced functionality of mucociliary clearance and weakening of alveolar macrophages. This injury can be split into three categories:

1. Heat Injury to the Upper Airway

The greatest complication of a heat injury to the upper airway is an obstruction due to extensive swelling of the the tongue, epiglottis, and aryepiglottic folds. The burns do not commonly extend into the lower airway as the larynx reflexively closes and the heat dissipates as air is not a good heat conductor. Swelling can take a few hours to develop, thus it is recommended to regularly assess the airway as an initial evaluation often changes. and accompanying obstruction. It takes a period of hours for airway swelling to develop as fluid resuscitation is taking place. It is important to note that initial evaluation might not be the best indicator of the extent of the obstruction that may later occur.

2. Chemical Injury to the Lower Airways

3. Systemic Toxicity due to Carbon Monoxide or Cyanide Exposure

For more information, please see Inhalation Injury

6. Friction Burn

A Friction Burn is an abrasion that occurs when the skin rubs against another surface. A Friction Burn is not a true burn, but because friction can generate heat, when an extreme case is seen, a patient will present with burns to the outer layer of the skin. Common causes are rope burn, rug burn, chafing or skinning.

Burn Classification

Burns can be classified according to their severity or depth. The characteristics of a burn can vary in amount of pain and colour of burn. depend upon its depth. Always be the on the look out for signs of inhalation burns, which are commonly burns around the mouth or nose. burns may have many complications and can cause shortness of breath, hoarseness of the voice, and stridor (noisy breathing to to airflow obstruction) or wheezing. Common symptoms are itchiness, as this is a sign of the healing process, and numbness or tingling following an electrical injury. Burns can have a large impact on an individuals mental health and his should always be taken into consideration.

Classification by Depth

Type	Layers Involved	Signs and Symptoms	Healing Time	Prognosis and Complications
First-Degree / Superficial	Epidermis	Red Dry Pain No blisters	5–10 days	Heals well. Repeated sunburns increase the risk of skin cancer later in life.
Second-Degree / Superficial Partial Thickness	Epidermis and can extend into the superficial dermis	Redness with a clear blister. Blanches with pressure but shows rapid capillary refill when released. Generally moist Very painful	2–3 weeks	Local infection (cellulitis) but no scarring typically
Second-Degree / Deep Partial Thickness	Extends into deep (reticular) dermis Often causes damage to the hair follicle and glandular tissue	Appears yellow or white. Less blanching than superficial. Very painful to pressure and uncomfortable Blisters are common Often moist and waxy Occasionally dry and may appear ivory or pearly white	3–8 weeks	Scarring, contractures (may require excision and skin grafting)
Third-Degree / Full Thickness	Extends through entire dermis and can often affect the underlying subcutaneous tissue	Appearance can vary from waxy white, leathery grey or charred black. Skin is dry, lacking in elasticity No blanching Not painful (nerve ending damage is common) Stiff and white/brown. No blanching.	Prolonged (months) and unfinished/incomplete	Eschar, or the dead, denatured skin, is removed. Results in scarring, contractures and amputation (early excision recommended) Cannot heal without surgery.
Fourth-Degree	Extends through entire skin, and into underlying fat, muscle and bone	Black; charred with eschar Dry No elasticity Painless	Does not heal; Requires excision	Amputation, significant functional impairment and in some cases, death.

Classification by Size

The Parkland Burn Formula is the most widely used formula to estimate the fluid resuscitation required by a burns patient on hospital admission, usually within the first 24 hours. When applying this formula, the first step is to calculate the percentage of body surface area (BSA) damaged, which is most commonly done by the "Wallace Rule of Nines". When conducting a pediatric assessment, the Lund-Browder Method is commonly used, due to the greater percentage surface area of their head and neck as compared to an adult. The formula recommends 4 milliliters per kilogram of body weight in adults (3 milliliters per kilogram in children) per percentage burn of total body surface area (%TBSA) of crystalloid solution over the first 24 hours of care.

4 mL/kg/%TBSA (3 mL/kg/%TBSA in children) = total amount of crystalloid fluid during first 24 hours

The latest research has indicated that while this method is still in use, the fluid levels should be constantly monitored, while assessing the urine output, to prevent over-resuscitation or under-resuscitation.

The Rule of Nine and Lund-Browder Method Percentages

Body Part	Percentage for Rule of Nine	Percentage for Lund-Browder Method
Head and Neck	9%	18%
Entire chest	9%	9%
Entire abdomen	9%	9%
Entire back	18%	18%
Lower Extremity	18% each	13.5%
Upper Extremity	9% each	9% each
Groin	1%	1%

Palmar Surface Method

The "Rule of Palm" or Palmar Surface Method can be used to estimate body surface area of a burn. This rule indicates that the palm of the patient, with the exclusion of the fingers and wrist, is approximately 1% of the patients body surface area. When a quick estimate is required, the percentage body surface area will be the number of the patients' own palm it would take to cover their injury. It is important to use the patients palm and not the providers palm.

Local Effect of Burns

This occurs immediately after the injury and the burn wound can be divided into three zones.

• Zone of Coagulation: This is the area central to the injury and is the area that suffers the greatest tissue damage.

• Zone of Stasis or Zone of Ischemia: This area is adjacent to the zone of coagulation and as the name suggests, it is a zone in which the there is slowing of circulating blood due to the damage. This zone can usually be saved with the correct wound care.

• Zone of Hyperemia: This zone is circumferential and is characterised by the eased blood supply and inflammatory vasodilation. This tissue has a good recovery rate, as long as there are no complications, such as severe sepsis or prolonged hypo-perfusion.

This video describes the pathophysiology of Burns